Deinococcus arenicola sp. nov., a novel radiation-resistant bacterium isolated from sandy soil in Antarctica.

A Gram-stain-positive, aerobic, non-mobile and spherical strain, designated ZS9-10T, belonging to the genus Deinococcus was isolated from soil sampled at the Chinese Zhong Shan Station, Antarctica. Growth was observed in the presence of 0-4 % (w/v) NaCl, at pH 7.0-8.0 and at 4-25 °C. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain ZS9-10T formed a lineage in the genus Deinococcus. It exhibited highest sequence similarity (97.4 %) to Deinococcus marmoris DSM 12784T. The major phospholipids of ZS9-10T were unidentified phosphoglycolipid, unidentified glycolipids and unidentified lipids. The major fatty acids were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C16 : 0 and C16 : 1 ω7c. MK-8 was the predominant respiratory quinone. The digital DNA-DNA hybridization and average nucleotide identity values between strain ZS9-10T and its close relative D. marmoris DSM 12784T were 27.4 and 83.9 %, respectively. Based on phenotypic, phylogenetic and genotypic data, a novel species, named Deinococcus arenicola sp. nov., is proposed. The type strain iis ZS9-10T (=CCTCC AB 2019392T=KCTC43192T).

Short-term impacts of polyethylene and polyacrylonitrile microplastics on soil physicochemical properties and microbial activity of a marine terrace environment in maritime Antarctica.

Evidence of microplastic (MP) pollution in Antarctic terrestrial environments reinforces concerns about its potential impacts on soil, which plays a major role in ecological processes at ice-free areas. We investigated the effects of two common MP types on soil physicochemical properties and microbial responses of a marine terrace from Fildes Peninsula (King George Island, Antarctica). Soils were treated with polyethylene (PE) fragments and polyacrylonitrile (PAN) fibers at environmentally relevant doses (from 0.001% to 1% w w-1), in addition to a control treatment (0% w w-1), for 22 days in a pot incubation experiment under natural field conditions. The short-term impacts of MPs on soil physical, chemical and microbial attributes seem interrelated and were affected by both MP dose and type. The highest PAN fiber dose (0.1%) increased macro and total porosity, but decreased soil bulk density compared to control, whereas PE fragments treatments did not affect soil porosity. Soil respiration increased with increasing doses of PAN fibers reflecting impacts on physical properties. Both types of MPs increased microbial activity (fluorescein diacetate hydrolysis), decreased the cation exchange capacity but, especially PE fragments, increased Na+ saturation. The highest dose of PAN fibers and PE fragments increased total nitrogen and total organic carbon, respectively, and both decreased the soil pH. We discussed potential causes for our findings in this initial assessment and addressed the need for further research considering the complexity of environmental factors to better understand the cumulative impacts of MP pollution in Antarctic soil environments.

Biogeographic survey of soil bacterial communities across Antarctica.

BACKGROUND: Antarctica and its unique biodiversity are increasingly at risk from the effects of global climate change and other human influences. A significant recent element underpinning strategies for Antarctic conservation has been the development of a system of Antarctic Conservation Biogeographic Regions (ACBRs). The datasets supporting this classification are, however, dominated by eukaryotic taxa, with contributions from the bacterial domain restricted to Actinomycetota and Cyanobacteriota. Nevertheless, the ice-free areas of the Antarctic continent and the sub-Antarctic islands are dominated in terms of diversity by bacteria. Our study aims to generate a comprehensive phylogenetic dataset of Antarctic bacteria with wide geographical coverage on the continent and sub-Antarctic islands, to investigate whether bacterial diversity and distribution is reflected in the current ACBRs. RESULTS: Soil bacterial diversity and community composition did not fully conform with the ACBR classification. Although 19% of the variability was explained by this classification, the largest differences in bacterial community composition were between the broader continental and maritime Antarctic regions, where a degree of structural overlapping within continental and maritime bacterial communities was apparent, not fully reflecting the division into separate ACBRs. Strong divergence in soil bacterial community composition was also apparent between the Antarctic/sub-Antarctic islands and the Antarctic mainland. Bacterial communities were partially shaped by bioclimatic conditions, with 28% of dominant genera showing habitat preferences connected to at least one of the bioclimatic variables included in our analyses. These genera were also reported as indicator taxa for the ACBRs. CONCLUSIONS: Overall, our data indicate that the current ACBR subdivision of the Antarctic continent does not fully reflect bacterial distribution and diversity in Antarctica. We observed considerable overlap in the structure of soil bacterial communities within the maritime Antarctic region and within the continental Antarctic region. Our results also suggest that bacterial communities might be impacted by regional climatic and other environmental changes. The dataset developed in this study provides a comprehensive baseline that will provide a valuable tool for biodiversity conservation efforts on the continent. Further studies are clearly required, and we emphasize the need for more extensive campaigns to systematically sample and characterize Antarctic and sub-Antarctic soil microbial communities. Video Abstract.

Evaluation of the Deterioration of Untreated Commercial Polystyrene by Psychrotrophic Antarctic Bacterium.

Polystyrene (PS) and microplastic production pose persistent threats to the ecosystem. Even the pristine Antarctic, which is widely believed to be pollution-free, was also affected by the presence of microplastics. Therefore, it is important to comprehend the extent to which biological agents such as bacteria utilise PS microplastics as a carbon source. In this study, four soil bacteria from Greenwich Island, Antarctica, were isolated. A preliminary screening of the isolates for PS microplastics utilisation in the Bushnell Haas broth was conducted with the shake-flask method. The isolate AYDL1 identified as Brevundimonas sp. was found to be the most efficient in utilising PS microplastics. An assay on PS microplastics utilisation showed that the strain AYDL1 tolerated PS microplastics well under prolonged exposure with a weight loss percentage of 19.3% after the first interval (10 days of incubation). Infrared spectroscopy showed that the bacteria altered the chemical structure of PS while a deformation of the surface morphology of PS microplastics was observed via scanning electron microscopy after being incubated for 40 days. The obtained results may essentially indicate the utilisation of liable polymer additives or "leachates" and thus, validate the mechanistic approach for a typical initiation process of PS microplastics biodeterioration by the bacteria (AYDL1)-the biotic process.

Cryobacterium zhongshanensis sp. nov., an actinobacterium isolated from Antarctic soil.

A Gram-staining-positive, heterotrophic, non-spore-forming, non-motile, rod-shaped, strain ZS14-85T belonging to the genus Cryobacterium was isolated from soil in Antarctica. Growth was observed in the presence of 0-2% (w/v) NaCl, at pH 7.0-9.0 (optimum, pH 7.0) and 4-30 ℃ (optimum, 20 ℃). Phylogenetic analysis showed that strain ZS14-85T formed a lineage in the genus Cryobacterium. The digital DNA-DNA hybridization (dDDH) values between strain ZS14-85T and its close relatives Cryobacterium psychrotolerans CGMCC 1.5382T, Cryobacterium soli MCCC 1K03549T and Cryobacterium breve NBRC 113800T were 22.5, 22.3 and 22.2%, respectively. Orthologous Average Nucleotide Identity (OrthoANI) scores between strain ZS14-85T and C. psychrotolerans CGMCC 1.5382T, C. breve NBRC 113800T and C. soli MCCC 1K03549T were 78.7, 78.1 and 77.7%, respectively. The polar lipids of strain ZS14-85T were diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), one unidentified glycolipid (GL) and two unidentified lipids (L). The major fatty acids were anteiso-C15:0 (60.7%), iso-C16:0 (17.0%) and anteiso-C17:0 (15.2%). MK-10, MK-11 and MK-9 were the predominant respiratory menaquinones. Based on phenotypic, phylogenetic and genotypic data, a novel species, Cryobacterium zhongshanensis sp. nov. is proposed. The type strain is ZS14-85T (= CCTCC AB 2019396T = KCTC 49384T).

Manganese-Oxidizing Antarctic Bacteria (Mn-Oxb) Release Reactive Oxygen Species (ROS) as Secondary Mn(II) Oxidation Mechanisms to Avoid Toxicity.

Manganese (Mn) oxidation is performed through oxidative Mn-oxidizing bacteria (MnOxb) as the main bio-weathering mechanism for Mn(III/IV) deposits during soil formation. However, with an increase in temperature, the respiration rate also increases, producing Reactive Oxygen Species (ROS) as by-products, which are harmful to microbial cells. We hypothesize that bacterial ROS oxidize Mn(II) to Mn(III/IV) as a secondary non-enzymatic temperature-dependent mechanism for cell protection. Fourteen MnOxb were isolated from Antarctic soils under the global warming effect, and peroxidase (PO) activity, ROS, and Mn(III/IV) production were evaluated for 120 h of incubation at 4 °C, 15 °C, and 30 °C. ROS contributions to Mn oxidation were evaluated in Arthrobacter oxydans under antioxidant (Trolox) and ROS-stimulated (menadione) conditions. The Mn(III/IV) concentration increased with temperature and positively correlated with ROS production. ROS scavenging with Trolox depleted the Mn oxidation, and ROS-stimulant increased the Mn precipitation in A. oxydans. Increasing the Mn(II) concentration caused a reduction in the membrane potential and bacterial viability, which resulted in Mn precipitation on the bacteria surface. In conclusion, bacterial ROS production serves as a complementary non-enzymatic temperature-dependent mechanism for Mn(II) oxidation as a response in warming environments.

Actinobacteria and Cyanobacteria Diversity in Terrestrial Antarctic Microenvironments Evaluated by Culture-Dependent and Independent Methods.

Bacterial diversity from McMurdo Dry Valleys in Antarctica, the coldest desert on earth, has become more easily assessed with the development of High Throughput Sequencing (HTS) techniques. However, some of the diversity remains inaccessible by the power of sequencing. In this study, we combine cultivation and HTS techniques to survey actinobacteria and cyanobacteria diversity along different soil and endolithic micro-environments of Victoria Valley in McMurdo Dry Valleys. Our results demonstrate that the Dry Valleys actinobacteria and cyanobacteria distribution is driven by environmental forces, in particular the effect of water availability and endolithic environments clearly conditioned the distribution of those communities. Data derived from HTS show that the percentage of cyanobacteria decreases from about 20% in the sample closest to the water source to negligible values on the last three samples of the transect with less water availability. Inversely, actinobacteria relative abundance increases from about 20% in wet soils to over 50% in the driest samples. Over 30% of the total HTS data set was composed of actinobacterial strains, mainly distributed by 5 families: Sporichthyaceae, Euzebyaceae, Patulibacteraceae, Nocardioidaceae, and Rubrobacteraceae. However, the 11 actinobacterial strains isolated in this study, belonged to Micrococcaceae and Dermacoccaceae families that were underrepresented in the HTS data set. A total of 10 cyanobacterial strains from the order Synechococcales were also isolated, distributed by 4 different genera (Nodosilinea, Leptolyngbya, Pectolyngbya, and Acaryochloris-like). In agreement with the cultivation results, Leptolyngbya was identified as dominant genus in the HTS data set. Acaryochloris-like cyanobacteria were found exclusively in the endolithic sample and represented 44% of the total 16S rRNA sequences, although despite our efforts we were not able to properly isolate any strain from this Acaryochloris-related group. The importance of combining cultivation and sequencing techniques is highlighted, as we have shown that culture-dependent methods employed in this study were able to retrieve actinobacteria and cyanobacteria taxa that were not detected in HTS data set, suggesting that the combination of both strategies can be usefull to recover both abundant and rare members of the communities.

Kaistella gelatinilytica sp. nov., a flavobacterium isolated from Antarctic soil.

A Gram-stain-negative, aerobic, non-spore-forming, rod-shaped, non-motile, yellow-pigmented bacteria, designated strain G5-32T, belonging to the genus Kaistella was isolated from soil collected in the Antarctic. The strain was identified using a polyphasic taxonomic approach. The strain grew in the presence of 0-5% (w/v) NaCl (optimum, 1%), at pH 6.0-9.0 (optimum, pH 8.0) and at 4-28 °C (optimum, 20 °C). The predominant menaquinone was MK-6 (99.4%). The major fatty acids were anteiso-C15:0 (28.2%), iso-C15:0 (16.4%), summed feature 9 (comprising iso-C17:1 ω9c and/or 10-methyl C16:0; 10.6%) and iso-C16:0 (5.9%). A phylogenetic tree based on 16S rRNA gene sequences showed that strain G5-32T formed a lineage within the genus Kaistella with the closest phylogenetic neighbours Kaistella yonginensis HMD1043T, Kaistella chaponensis DSM 23145T, Kaistella jeonii DSM 17048T and Kaistella carnis NCTC 13525T (97.9, 97.8, 97.8 and 98.0 % 16S rRNA gene sequence similarity, respectively). The ANI values between strain G5-32T and K. jeonii DSM 17048T, K. chaponensis DSM 23145T, K. carnis NCTC 13525T and K. yonginensis HMD1043T were 90.9, 82.6, 77.1 and 76.3%. Concurrently, digital DNA-DNA hybridization values of strain G5-32T assessed against K. jeonii DSM 17048T, K. chaponensis DSM 23145T, K. carnis NCTC 13525T and K. yonginensis HMD1043T were 42.3, 25.9, 21.7 and 21.3%, respectively. Based on phenotypic, phylogenetic and genotypic data, a novel species, Kaistella gelatinilytica sp. nov., is proposed. The type strain is G5-32T (=CCTCC AA 2019083T=KCTC 72766T).

Passive warming effect on soil microbial community and humic substance degradation in maritime Antarctic region.

Although the maritime Antarctic has undergone rapid warming, the effects on indigenous soil-inhabiting microorganisms are not well known. Passive warming experiments using open-top chamber (OTC) have been performed on the Fildes Peninsula in the maritime Antarctic since 2008. When the soil temperature was measured at a depth of 2-5 cm during the 2013-2015 summer seasons, the mean temperature inside OTC (OTC-In) increased by approximately 0.8 °C compared with outside OTC (OTC-Out), while soil chemical and physical characteristics did not change. Soils (2015 summer) from OTC-In and OTC-Out were subjected to analysis for change in microbial community and degradation rate of humic substances (HS, the largest pool of recalcitrant organic carbon in soil). Archaeal and bacterial communities in OTC-In were minimally affected by warming compared with those in OTC-Out, with archaeal methanogenic Thermoplasmata slightly increased in abundance. The abundance of heterotrophic fungi Ascomycota was significantly altered in OTC-In. Total bacterial and fungal biomass in OTC-In increased by 20% compared to OTC-Out, indicating that this may be due to increased microbial degradation activity for soil organic matter (SOM) including HS, which would result in the release of more low-molecular-weight growth substrates from SOM. Despite the effects of warming on the microbial community over the 8-years-experiments warming did not induce any detectable change in content or structure of polymeric HS. These results suggest that increased temperature may have significant and direct effects on soil microbial communities inhabiting maritime Antarctic and that soil microbes would subsequently provide more available carbon sources for other indigenous microbes.

Flavobacterium phocarum sp. nov., isolated from soils of a seal habitat in Antarctica.

A Gram-stain-negative, yellow-pigmented, non-flagellated, gliding, rod-shaped, oxidase-negative and catalase-positive bacterium, designated SE14T, was isolated from soil on King George Island, South Shetland Islands, Antarctica. Strain SE14T grew at 4-25 °C (optimum, 20 °C), at pH 6.0-9.0 (optimum, pH 7.0-7.5) and with 0-3.0 % NaCl (optimum, 1.0-1.5 %), and could not produce flexirubin-type pigments. 16S rRNA gene sequence analysis showed the the isolate belonged to the genus Flavobacterium. Strain SE14T had the highest 16S rRNA gene sequence similarity to Flavobacterium antarcticum, F. tegetincola and F. degerlachei with 95.8, 95.5 and 95.2 %, respectively. The strain SE14T consisted of a clade with Flavobacteriumnoncentrifugens (16S rRNA gene sequence similarity 94.9 %) and F. qiangtangense (16S rRNA gene sequence similarity 94.2 %) and simultaneously formed a distinct phyletic lineage in the neighbour-joining phylogenetic tree. Polar lipids of the strain included phosphatidylethanolamine and four unidentified aminolipids. Strain SE14T contained anteiso-C15 : 0, iso-C15 : 0 and a mixture of iso-C15 : 0 2-OH and/or C16 : 1ω7c as the main fatty acids, and the only respiratory quinone was menaquinone-6. The genomic DNA G+C content was 42.3 mol%. The polyphasic taxonomic study revealed that strain SE14T belongs to a novel species within the genus Flavobacterium , and the name Flavobacterium phocarum sp. nov. is proposed. The type strain is SE14T (=CCTCC AB 2017225T=KCTC 52612T).

Flavobacterium ardleyense sp. nov., isolated from Antarctic soil.

A Gram-stain-negative, aerobic, yellow-pigmented, non-flagellated, non-gliding, rod-like, oxidase- and catalase-positive bacterium, designated A2-1T, was isolated from soil on Ardley Island, South Shetland Islands, Antarctica. Strain A2-1T grew at 4-22 °C (optimum, 10 °C), at pH 6.0-8.0 (optimum, pH 6.5) and with 0-1.5 % NaCl (optimum, 0.5 %), but could not produce flexirubin-type pigments. 16S rRNA gene sequence analysis showed that the isolates belonged to the genus Flavobacterium. Strain A2-1T had the highest 16S rRNA gene sequence similarity to Flavobacterium cucumis, F. ahnfeltiae and F. cheniae with 95.7, 95.6 and 95.4 %, respectively. The strain A2-1T consisted of a clade with F. cucumis and F. cheniae and simultaneously formed a distinct phyletic lineage in the neighbour-joining phylogenetic tree. Polar lipids of the strain included phosphatidylethanolamine (PE), four unidentified aminolipids and one unidentified lipid. The strain A2-1T contained anteiso-C15 : 0 (20.2 %), iso-C15 : 0 (16.2 %) and C15 : 1 G (11.0 %) as the main fatty acids and the only respiratory quinone was menaquinone MK-6. The genomic DNA G+C content was 34.0 mol%. The polyphasic taxonomic study revealed that the strain A2-1T belongs to a novel species within the genus Flavobacterium and the name Flavobacterium ardleyense sp. nov. is proposed. The type strain is A2-1T (=CCTCC AB 2017157T=KCTC 52644T).

Pseudomonas versuta sp. nov., isolated from Antarctic soil.

In this study we analysed three bacterial strains coded L10.10T, A4R1.5 and A4R1.12, isolated in the course of a study of quorum-quenching bacteria occurring in Antarctic soil. The 16S rRNA gene sequence was identical in the three strains and showed 99.7% pairwise similarity with respect to the closest related species Pseudomonas weihenstephanensis WS4993T. Therefore, the three strains were classified within the genus Pseudomonas. Analysis of housekeeping genes (rpoB, rpoD and gyrB) sequences showed similarities of 84-95% with respect to the closest related species of Pseudomonas, confirming its phylogenetic affiliation. The ANI values were less than 86% to the closest related species type strains. The respiratory quinone is Q9. The major fatty acids are C16:0, C16:1 ω7c/ C16:1 ω6c in summed feature 3 and C18:1 ω7c / C18:1 ω6c in summed feature 8. The strains are oxidase- and catalase-positive. Growth occurs at 4-30°C, and at pH 4.0-10. The DNA G+C content is 58.2-58.3mol %. The combined genotypic, phenotypic and chemotaxonomic data support the classification of strains L10.10T, A4R1.5 and A4R1.12 into a novel species of Pseudomonas, for which the name P. versuta sp. nov. is proposed. The type strain is L10.10T (LMG 29628T, DSM 101070T).

Microbial Diversity of Browning Peninsula, Eastern Antarctica Revealed Using Molecular and Cultivation Methods.

Browning Peninsula is an ice-free polar desert situated in the Windmill Islands, Eastern Antarctica. The entire site is described as a barren landscape, comprised of frost boils with soils dominated by microbial life. In this study, we explored the microbial diversity and edaphic drivers of community structure across this site using traditional cultivation methods, a novel approach the soil substrate membrane system (SSMS), and culture-independent 454-tag pyrosequencing. The measured soil environmental and microphysical factors of chlorine, phosphate, aspect and elevation were found to be significant drivers of the bacterial community, while none of the soil parameters analyzed were significantly correlated to the fungal community. Overall, Browning Peninsula soil harbored a distinctive microbial community in comparison to other Antarctic soils comprised of a unique bacterial diversity and extremely limited fungal diversity. Tag pyrosequencing data revealed the bacterial community to be dominated by Actinobacteria (36%), followed by Chloroflexi (18%), Cyanobacteria (14%), and Proteobacteria (10%). For fungi, Ascomycota (97%) dominated the soil microbiome, followed by Basidiomycota. As expected the diversity recovered from culture-based techniques was lower than that detected using tag sequencing. However, in the SSMS enrichments, that mimic the natural conditions for cultivating oligophilic "k-selected" bacteria, a larger proportion of rare bacterial taxa (15%), such as Blastococcus, Devosia, Herbaspirillum, Propionibacterium and Methylocella and fungal (11%) taxa, such as Nigrospora, Exophiala, Hortaea, and Penidiella were recovered at the genus level. At phylum level, a comparison of OTU's showed that the SSMS shared 21% of Acidobacteria, 11% of Actinobacteria and 10% of Proteobacteria OTU's with soil. For fungi, the shared OTUs was 4% (Basidiomycota) and <0.5% (Ascomycota). This was the first known attempt to culture microfungi using the SSMS which resulted in an increase in diversity from 14 to 57 microfungi OTUs compared to standard cultivation. Furthermore, the SSMS offers the opportunity to retrieve a greater diversity of bacterial and fungal taxa for future exploitation.

Planococcus versutus sp. nov., isolated from soil.

A taxonomic study was performed on a novel Gram-stain-positive, coccus-shaped, orange-pigmented motile bacterium, designated as strain L10.15T. The organism was isolated from a soil sample collected in Lagoon Island (close to Adelaide Island, western Antarctic Peninsula) using a quorum-quenching enrichment medium. Growth occurred at 4-30 °C, pH 6-11 and at moderately high salinity (0-15 %, w/v, NaCl), with optimal growth at 26 °C, at pH 7-8 and with 6 % (w/v) NaCl. 16S rRNA gene sequence analysis showed that strain L10.15T belonged to the genus Planococcus and was closely related to Planococcus halocryophilus Or1T (99.3 % similarity), Planococcus donghaensis JH1T (99.0 %), Planococcus antarcticus DSM 14505T (98.3 %), Planococcus plakortidis AS/ASP6 (II)T (97.6 %), Planococcus maritimus TF-9T (97.5 %), Planococcus salinarum ISL-6T (97.5 %) and Planococcus kocurii NCIMB 629T (97.5 %). However, the average nucleotide identity-MUMmer analysis showed low genomic relatedness values of 71.1-81.7 % to the type strains of these closely related species of the genus Planococcus. The principal fatty acids were anteiso-C15 : 0, C16 : 1ω7c and anteiso-C17 :  0, and the major menaquinones of strain L10.15T were MK-5 (48 %), MK-6 (6 %) and MK-7 (44 %). Polar lipid analysis revealed the presence of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and aminophospholipid. The DNA G+C content was 39.4 mol%. The phenotypic and genotypic data indicate that strain L10.15T represents a novel species of the genus Planococcus, for which the name Planococcus versutus sp. nov. is proposed. The type strain is L10.15T (=DSM 101994T=KACC 18918T).

The genome of the Antarctic polyextremophile Nesterenkonia sp. AN1 reveals adaptive strategies for survival under multiple stress conditions.

Nesterenkonia sp. AN1 is a polyextremophile isolated from Antarctic desert soil. Genomic analyses and genome comparisons with three mesophilic Nesterenkonia strains indicated that the unique genome fraction of Nesterenkonia sp. AN1 contains adaptive features implicated in the response to cold stress including modulation of membrane fluidity as well as response to cold-associated osmotic and oxidative stress. The core genome also encodes a number of putative cold stress response proteins. RNA-Seq-based transcriptome analyses of Nesterenkonia sp. AN1 grown at 5ºC and 21°C showed that there was significant induction of transcripts that code for antioxidants at 5ºC, demonstrated by the upregulation of sodA, bcp and bpoA2. There was also overexpression of universal stress protein genes related to uspA, along with genes encoding other characterized cold stress features. Genes encoding the two key enzymes of the glyoxylate cycle, isocitrate lyase (ICL) and malate synthase (AceB) were induced at 5ºC, suggesting possible adaptation strategies for energy metabolism in cold habitats. These genomic features may contribute to the survival of Nesterenkonia sp. AN1 in arid Antarctic soils.

A novel bacterial Water Hypersensitivity-like protein shows in vivo protection against cold and freeze damage.

Metagenomic library screening, by functional or sequence analysis, has become an established method for the identification of novel genes and gene products, including genetic elements implicated in microbial stress response and adaptation. We have identified, using a sequence-based approach, a fosmid clone from an Antarctic desert soil metagenome library containing a novel gene which codes for a protein homologous to a Water Hypersensitivity domain (WHy). The WHy domain is typically found as a component of specific LEA (Late Embryogenesis Abundant) proteins, particularly the LEA-14 (LEA-8) variants, which occur widely in plants, nematodes, bacteria and archaea and which are typically induced by exposure to stress conditions. The novel WHy-like protein (165 amino acid, 18.6 kDa) exhibits a largely invariant NPN motif at the N-terminus and has high sequence identity to genes identified in Pseudomonas genomes. Expression of this protein in Escherichia coli significantly protected the recombinant host against cold and freeze stress.

Production of cold-adapted cellulase by Verticillium sp. isolated from Antarctic soils

Background: Cellulose can be converted to ethanol by simultaneous saccharification and fermentation (SSF). The difference between the optimal temperature of cellulase and microbial fermentation, however, has been identified as the critical problem with SSF. In this study, one fungal strain (AnsX1) with high cellulase activity at low temperature was isolated from Antarctic soils and identified as Verticillium sp. by morphological and molecular analyses. Results: The biochemical properties of crude AnsX1 cellulase samples were studied by filter paper cellulase assay. The maximum cellulase activity was achieved at low temperature in an acidic environment with addition of metal ions. Furthermore, AnsX1 cellulase demonstrated 54-63% enzymatic activity at ethanol concentrations of 5-10%. AnsX1 cellulase production was influenced by inoculum size, carbon and nitrogen sources, and elicitors. The optimal culture conditions for AnsX1 cellulase production were 5% inoculum, wheat bran as carbon source, (NH4)2SO4 as nitrogen source, and sorbitol added in the medium. Conclusions: Our present work has potential to enable the development of an economic and efficient cold-adapted cellulase system for bioconversion of lignocellulosic biomass into biofuels in future.